The present invention relates to an automatic sheet feeder for a printer capable of selectively printing continuous paper and cut sheets.
A printer of this type includes a printer body and an automatic sheet feeder, detachably arranged on the printer body, for feeding cut sheets to the printer body. The printer body includes a tractor for conveying continuous paper to a printing mechanism, and a case for covering these parts. The case includes an upper wall in which a paper discharge port and a cut sheet supply port are formed, and a rear wall in which a continuous paper supply port is formed. When continuous paper is to be printed on, the automatic sheet feeder is first of all detached from the printer body, so as not to interfere with the discharge of the continuous paper. Following printing, the continuous paper is then inserted into the case, through the continuous paper supply port, and then conveyed to the printing mechanism by the tractor. The printed continuous paper is discharged from the case through the paper discharge port, and conveyed along the upper wall to behind the case.
When a cut sheet is to be printed on, the automatic sheet feeder is mounted on the upper wall of the case, to cover the cut sheet supply port and paper discharge port. The cut sheets stacked in a cassette incorporated in the sheet feeder are fed one by one by a feed roller, through the cut sheet supply port, to the printing mechanism inside the case. The printed-on cut sheets are guided through the paper discharge port of the case, back into the sheet feeder, and stacked, by a discharge roller, at a predetermined location therewithin.
Thus, in the case of the above printer, the automatic sheet feeder having a mechanism for feeding cut sheets is selectively mounted on the printer body having a mechanism for feeding continuous paper, thereby enabling printing on continuous paper or cut sheets. However, this means that the automatic sheet feeder must be alternately mounted and detached, depending on the printing mode--for continuous paper or for cut sheets --selected. Frequent changes in printing mode make this operation both cumbersome and time-consuming. Furthermore, additional space is required for storing the automatic sheet feeder when it is detached from the printer.
With the aim of solving the above-described problems, a printer has been proposed in which continuous paper is printed without the need to detach an automatic sheet feeder from the printer body, the printed-on continuous paper being discharged from the printer through the inside of the automatic sheet feeder. In this case, however, the following problems arise: The continuous paper is pulled by the discharging mechanism of the automatic sheet feeder while, at the same time, being pushed by the feeding mechanism of the printer body. Since the operations of the feeding and discharging mechanisms are not perfectly synchronized, the precision regarding feeding of the continuous paper is degraded. As a result, the printing position (carriage return position) is shifted from that desired, and hence accurate printing cannot be performed. Furthermore, when continuous paper is discharged through the inside of the automatic sheet feeder, the continuous paper tends to be caught by, for example, the cut sheet cassette or a discharged paper stacker. Consequently, it is difficult to smoothly discharge the printed-on continuous paper. In addition, since the paper discharge port is blocked by the automatic sheet feeder, printed continuous paper cannot be cut off at a position immediately after the printed-on portion, i.e., close to the printing mechanism.